Not Applicable
1. Field of the Invention
This invention relates to a meal rendering process and apparatus. More particularly, the present invention relates to a process and apparatus that facilitates efficient recovery of particulate matter which becomes airborne as a result of a product being exposed to industrial cooling or drying processes. An example of such a cooling or drying process is during the rendering process and production of meat meal, where the meat product is heated to a temperature of approximately 270 degrees Fahrenheit The meat meal product is extruded or pressed and is placed into a counter air flow cooler which draws a counter flowing air stream over the meat meal product thereby reducing the temperature of the meat product to approximately 130 degrees Fahrenheit. However, the air stream tends to draw a significant amount of particulate meat meal away from the cooling product. The suspended product, as picked up by the air stream, may be comprised of between 10 and 15 percent fat. The present invention is directed to the use of a unique negative air pressure separator which utilizes a self evacuating centrifugal separator and water blender, which when an air stream is drawn therethrough, will recover approximately 99.9 percent of any airborne particulate from the air steam. The present invention is particularly useful for separating viscous or sticky particulate, such as the aforementioned fat particulate, from an airstream without plugging or otherwise interfering with the functioning of the separator.
2. Description of the Related Art
As mentioned above, meat meal rendering processes are known which utilize high temperature cooking to remove bacteria and to soften meat, fat, bones, skin and the like. The rendering process generally produces a soft, pliable dry product which contains approximately 10 percent moisture content. Upon completion of the rendering process the dry product will have a temperature of approximately 260xc2x0 Fahrenheit (126xc2x0 Celsius) and a fat content of approximately 30 percent. The cooked product is then transferred to a press such as a tapered extruder where much of the fat content is squeezed out from the meat meal product through small holes in the press. However, pressing the meat meal alone is insufficient for extracting all of the fat content from the product as about 10 to 15 percent of the fat remains in the product.
In prior meat rendering processes, the heated and pressed meat meal product is typically moved to a cooler where it is exposed to a stream of ambient air which is intended to cool the meat product. Ambient air in contact with the meat meal within the cooler normally increases in temperature to over 200 degrees Fahrenheit before the air exits the cooler. The heat exchange between the air stream and the product also results in moisture being drawn away from the product, with the moisture being contained in the air stream well below the dew point. The particulate which remains in the air stream as it exits the cooler may be detected by people in the form of an unpleasant odor.
Devices have been used in conjunction with coolers in an attempt to prevent or control particulate build up and to remove particulate content from the air stream in a controlled manner. Devices such as a conventional centrifuge or cyclone, bag houses and other types of separators have been employed using a number of configurations and methods. Unfortunately these prior devices and methods fail to separate particulate from the air stream to a desired level of efficiency and fail to address the problems associated with particulate build up. For example the oily particulate tends to build up in cyclones forming oily plugs, the rotary air lock on the discharge of cyclones likewise plug. Oily particulates also tend to buildup on the interior walls of conventional centrifuge devices causing plugging. Furthermore, the oily nature of the product renders a bag house inoperable. In addition, because the prior systems fail to separate out a sufficient percentage of particulate from the air stream, odor emitted from expelled air continues to be a problem.
In many rendering systems, the aforementioned problems associated with ambient air coolers are avoided by merely not using a cooler with the rendering system. In such rendering processes the hot meal product is handled directly. As a result of direct handling of the product, condensation occurs around the product thereby providing a warm moist environment for bacterial growth, such as salmonella, to occur. Obviously, in such processes odor remains a significant problem.
In view of the foregoing it is clear that a separator is needed having the capability to efficiently and effectively capture the particulate that is picked up in the air stream of current rendering/cooling processes. A device is needed which provides the desired particulate separation efficiency and which may be added to existing meat rendering processes.
In view of the above, the present invention is directed to an apparatus and system which addresses the shortcomings of known meat meal rendering processes and associated apparatus, as generally known and described above. The present invention provides for a unique centrifugal separator and water blending chamber which may be utilized with a processing system such as the meat rendering system cooler described above or with other processing systems such as a hammer mill. In at least one embodiment of the invention, the present apparatus may be connected to a cooling system such as previously discussed by connecting the air stream outlet of the cooler to the centrifugal separator of the present invention. The centrifugal separator removes the majority of air borne particulate present in the air stream. Following the centrifugal separator, the air stream may then be directed through a separator plate and into a blender section where the air flow may be exposed or blended with water to encapsulate any particulate remaining in the air stream. The water with encapsulated particles may then be recycled through the cooler or other associated system.
The present invention is directed to a method and apparatus which uses a unique air stream centrifuge and water blender design which not only separates suspended particles from an air stream, but which also includes a means for removing the particles from the apparatus itself, thereby preventing buildup of separated material which could otherwise interfere with the operation of the separator. The present invention may be incorporated into existing rendering and/or cooling systems, replacing and/or supplementing prior separator mechanisms such as cyclones or bag houses.
The present invention is a negative pressure system which draws an air stream through a centrifugal chamber and a water blending chamber. In the centrifugal chamber a plurality of longitudinally mounted radially extending paddles rotate at high speed drawing the air stream into the chamber and forcing the air stream to circulate in a manner similar to a centrifuge. This centrifuge effect causes the majority of particulate suspended in the air stream to be separated out and to collect on the inside wall of the chamber. The circulating paddles effectively scrape the collecting particulate from the wall of the chamber preventing build up. The paddles themselves have a unique configuration which when rotating at speed provide the desired centrifugal effect upon the air stream without subjecting the air stream to disruptive turbulence. In addition, the paddles"" design is such that particulate tends not to collect or build up on the paddle surface. The rotating action of the paddles directs the scraped particulate matter through a gated aperture which extends the length of the chamber. The gate allows the scrapped particulate matter to be pushed out of the chamber when the gate is in the open position, thereby preventing continuous build up of particulate.
The scrapped particulate matter is gravity dropped from the gate and into a collection area where a trough screw advances the particulate matter to an outlet port. Initially, the particulate matter is dropped into a hopper 66, which serves as a collection area The trough screw 70, is proximate to the bottom of the hopper 66, and extends beyond the hopper 66, and into the horizontal chamber 68, which is preferably a tube. The transition of the hopper 66, into a tube of the horizontal chamber 68, facilitates the formation of a cylindrical plug and air seal for the meal cooler centrifugal separator. The trough screw 70, and the housing within which it is contained, are constructed and arranged such that the particulate matter is allowed to accumulate and form a plug which blocks air from entering the system. The plug is advanced and simultaneously maintained by the continuous build up of particulate matter behind the advancing plug. By plugging the outlet port in this manner the invention is able to maintain a negative pressure air flow without back drafting from the outside air. The matter which comprises the plug is continuously pushed to the exit and replaced by material that follows, thus assuring that no static material remains in the system. The plug system is utilized because the product is non free-flowing and is too high in fat content to work in a rotary air lock.
After the air stream has passed through the centrifugal chamber the air stream passes through a separator plate and into a water blending chamber or blender. The separator plate allows the air stream to pass therethrough but restricts passage of particulate thus providing for further particulate separation. Within the blender the air stream is passed through water which is injected into the blender through one or more water injection ports. The water is mixed with the air stream to encapsulate the remaining particulate in water, which is then passed out of the blender and into a collection tank. The water is mixed with the air stream with a plurality of paddles similar to those which are in the centrifugal chamber such as are described above.
After passing through the water blending chamber the air stream is directed onto water to encapsulate particles remaining in the air stream. The air stream is directed in this manner by a diverter plate or baffle which directs the air stream toward and/or onto the water thus encapsulating particles in the air stream which were previously wetted in the blender. Passage of the air stream over the water and particulate mixture provides an additional mixing opportunity between the water and air to separate any remaining particulate suspended in the air stream. The air stream is then pulled by a fan which releases the air stream into the atmosphere being approximately 99.9 percent or more particulate free. The water encapsulated particles may be pumped back to the cooler and injected onto the product as it passes through the cooler. Due to the high temperature of the meal product the water directed to the cooler will mostly evaporate thus depositing any particulate back into the product. This closed loop circulation of water allows the user to control and add moisture to the product as desired.
The present method and apparatus provides for a system which increases the efficiency of particulate collection and minimizes odor by removing most particles from the air stream. Additionally the present invention provides for a system which allows for moisture lost to a cooling, drying or other process to be replaced by recirculating moisture through a closed loop system for return to the original product during processing.
The present invention may be embodied in a variety of unique systems and apparatus such as those described in detail below. The invention may be retrofitted to an existing meal processor or may be included in new processor designs as well.